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Re: [zfs-discuss] Size discrepancy (beyond expected amount?)

Subject: Re: [zfs-discuss] Size discrepancy beyond expected amount?
From: Michael Ramchand
Date: Fri, 20 Mar 2009 09:31:41 +0000
You also DON'T want to give a single disk to your rpool. ZFS really needs to be able to fix errors when it finds them.

Suggest you read the ZFS Best Practices Guide (again). http://www.solarisinternals.com/wiki/index.php/ZFS_Best_Practices_Guide#Storage_Pools

Mike

Tomas Ögren wrote:
On 19 March, 2009 - Harry Putnam sent me these 1,4K bytes:

I'm finally getting close to the setup I wanted, after quite a bit of
experimentation and bugging these lists endlessly.

So first, thanks for your tolerance and patience.

My setup consists of 4 disks.  One holds the OS (rpool) and 3 more all
the same model and brand, all 500gb.

I've created a zpool in raidz1 configuration with:

  zpool create  zbk raidz1  c3d0 c4d0 c4d1

No errors showed up and zpool status shows no problems with those
three:
   pool: zbk
  state: ONLINE
  scrub: none requested
 config:

        NAME        STATE     READ WRITE CKSUM
        zbk         ONLINE       0     0     0
          raidz1    ONLINE       0     0     0
            c3d0    ONLINE       0     0     0
            c4d0    ONLINE       0     0     0
            c4d1    ONLINE       0     0     0


However, I appear to have lost an awfull lot of space... even above
what I expercted.

  df -h
[...]
  zbk                   913G   26K  913G   1% /zbk

It appears something like 1 entire disk is gobbled up by raidz1.

The same disks configured in zpool with no raidz1  shows  1.4tb with df.

I was under the impression raidz1 would take something like 20%.. but
this is more like 33.33%.

So, is this to be expected or is something wrong here?

Not a percentage at all.. raidz1 "takes" 1 disk. raidz2 takes 2 disks.
This is to be able to handle 1 vs 2 any-disk failures.

Then there's the 1000 vs 1024 factor as well. Your HD manufacturer says
500GB, the rest of the computer industry says ~465..

/Tomas


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